Body Fat Percentage vs. Body Mass Index (BMI)

As I trainer I often get asked “What measurement is more important for my overall health, body fat percentage or body mass index (BMI)?” While both measurements have value and serve a purpose, I believe as a society we pay too much attention to BMI and not enough attention on Body Fat Percentage. After the majority of my clients visit their family doctor, they inform me how much BMI was discussed while body fat percentage never entered the conversation. To some extent I understand this because BMI is much easier and quicker to measure, however, the focus needs to start shifting towards body fat percentage as a better indicator of overall health.

Before discussing the differences, we need to define both of these measurements. BMI is a weight-to-height ratio and is calculated by dividing weight (in kilograms) by the square of body height (in meters). Depending on the measurement you could be placed into one of four categories according to the CDC (listed below).

• Underweight: BMI<18.5

• Normal: 18.5-25

• Overweight: 25-30

• Obese: 30 and above

Body fat percentage is defined at the total mass of fat divided by the total body weight. The total fat mass includes essential body fat which is needed to survive, and body fat storage. According to the American Council of Exercise, below are the ranges and descriptions.

• Athletes: 6-13% (Male), 14-20% (Female)

• Fitness: 14-17% (Male), 21-24% (Female)

• Average: 18-24% (Male), 25-31% (Female)

• Obese: 25% and above (Male), 32% and above (Female)

Research and history has shown as both of these measurements increase, so does your risk for weight-related diseases. These diseases include heart disease, cancer, stroke, diabetes, as well as many other conditions commonly seen in the United States. If disease risk is positively correlated with a rise in both of these measurements, then assessing one’s overall health should include BMI and/or body fat percentage.

The debate between the two starts to creep in when talking about individuals that exercise on a regular basis.

If you are someone that does not exercise regularly, then BMI is an appropriate measurement when assessing overall health. For the rest of the population that is active daily, body fat percentage is superior because it takes into account your body composition. In other words, BMI only looks at your weight and height while body fat percentage measures fat and lean mass (i.e. muscle). BMI becomes misleading for many individuals who routinely perform strength training and carry a large amount of muscle mass. A lot of these individuals could fit the description of “fitness” or “athletes” in the body fat percentage table but considered overweight or obese according to their BMI measurement. If their body weight is higher than the average person because of a higher amount of muscle mass, then disease risk should not increase as muscle mass increases. Body fat is the problem when assessing disease risk and overall health, not the amount of muscle mass someone carries on their body.

Next time you get the chance, have an experienced health professional accurately measure your body fat percentage. This will give you a better overall picture of your health and help construct your fitness goals moving forward.